You can also "short stroke" the piston as well to gain a bit of ROF I have heard that removing 3 teeth is a pretty standard. Like others have said, M90 or "1 Joule" spring is also what you're looking for to get < 330 FPS. Then I guess you're done and can just play with it then reassess. If it's good then don't mess with it, if you feel the need for higher ROF then I guess you could run a high speed motor and high speed gears, the spring should be able to be pulled back by that setup especially considering you're running < 330 FPS.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE